Japanese Unexamined Patent Application Publication No. 2009-175824 (Patent Literature 1 (PLT 1)) discloses a main frame storage control device connected to a main frame and to other storage control device(s). The main frame storage control device converts commands and data received from the main frame into commands and data to be transmitted to the other storage control device(s). In addition, the main frame storage control device transmits data received from the other storage control device(s) to a host computer. It is thereby possible to provide the main frame with a plurality of real volumes as a single virtual volume.